System and method for determining fill volume in a container

ABSTRACT

A system and method for detecting a pathogen in a sample is provided, the system capable of measuring the volume of a sample in a container through the use of various measurement technologies, thereby ensuring that a user is aware of volumes not meeting specification and/or allowing correction of results to account for the out-of-specification sample.

This application claims priority to U.S. Provisional Application No.60/626,449, which was filed on Nov. 10, 2004.

CROSS-REFERENCE TO RELATED APPLICATIONS

Related subject matter is disclosed in U.S. Pat. No. 6,709,857 ofNicholas R. Bachur, Jr. et al. entitled “System And Method For OpticallyMonitoring The Concentration Of A Gas In A Sample Vial UsingPhotothermal Spectroscopy To Detect Sample Growth”, issued on Mar. 23,2004, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a system and method for pathogendetection via culture of a biological fluid.

2. Description of the Related Art

Many medical diagnoses require that a fluid sample, such as a bloodsample, be taken from a patient, cultured in a growth medium, and thenexamined for the presence of a pathogen believed to be causing thepatient's illness. The growth medium provides nutrients that allow thepathogen, such as a bacteria, virus, mycobacteria, mammalian cells orthe like, to multiply to a sufficient number so that their presence canbe detected.

In some cases, the pathogen can multiply to a large enough number sothat it can be detected visually. For example, a portion of the culturecan be placed on a microscope slide and visually examined to detect thepresence of a pathogen of interest.

Alternatively, the presence of a pathogen or other organism can bedetected indirectly by detecting the presence of byproducts given off bythe microorganism during its growth. For example, certain microorganismssuch as mammalian cells, insect cells, bacteria, viruses, mycobacteriaand fungi consume oxygen during their growth and life cycle. As thenumber of microorganisms increases in the sample culture, they naturallyconsume more oxygen. Furthermore, these oxygen consuming organismstypically release carbon dioxide as a metabolic byproduct. Accordingly,as the number of organisms present increases, the volume of carbondioxide that they collectively release likewise increases.

Several methods exist for measuring the increase of carbon dioxide in asample to determine whether organisms are present in the sample. Forexample, an instrument known as the Bactec® 9050 manufactured by BectonDickinson and Company detects changes in the color of an indicator todetermine whether carbon dioxide is present in a sample. That is, eachsample is collected in a respective sample vial containing an indicatormedium having a chemical that reacts to color change in the presence ofcarbon dioxide. A light sensor then detects the color of the indicatormedium in the sample vial when the sample vial is loaded into theinstrument. If the sample contains an organism which emits carbondioxide as a function of growth and/or metabolic activity, the reflectedor fluorescent intensity of the indicator medium will change in responseto the presence of the carbon dioxide. The light sensor will thereforedetect this change in intensity, and the instrument will indicate to anoperator that an organism is present in the sample contained in thesample vial. Other examples of instruments for detecting the presence oforganisms in a sample by measuring the changes in carbon dioxide in thesample are described in U.S. Pat. Nos. 4,945,060; 5,164,796; 5,094,955and 5,217,876, the entire content of each of these patents beingincorporated herein by reference.

Alternatively, instead of measuring the presence of carbon dioxide todetect the presence of an oxygen consuming microorganism, it is possibleto measure depletion in the concentration of oxygen in the sample ofinterest. In such a system, the sample vial includes an indicator whosecolor or fluorescence changes as the concentration of oxygen in the vialchanges. This change in color or fluorescence can be detected by aninstrument, which can provide an indication to a technician that oxygenin the sample is being depleted by an oxygen consuming organism withinthe sample. An instrument employing such an oxygen detecting techniqueis described in U.S. Pat. No. 5,567,598, the entire content of which isincorporated herein by reference.

The presence of oxygen consuming organisms can also be detected bymeasuring a change in the pressure in a sealed sample vial containingthe sample of interest. That is, as oxygen in a closed sample vial isdepleted by oxygen consuming organisms, the pressure in the sealedsample vial will change. The pressure will further change in the samplevial as the organisms emit carbon dioxide. Therefore, the presence ofsuch organisms can be detected by monitoring for changes in the pressurein the closed sample vial. Instruments that are capable of detectingsuch changes in pressure in the sample vial are described in U.S. Pat.Nos. 4,152,213; 5,310,658; 5,856,175 and 5,863,752, the entire contentof each of these patents being incorporated herein by reference.

While existing technology is effective, improvements are alwaysdesirable.

SUMMARY OF THE INVENTION

In one embodiment, the invention relates to a method for the detectionof a pathogen in a sample including the steps of, determining the volumeof the sample in a sample container comprising the sample and a growthmedium, then incubating the sample, and monitoring one or moreparameters in the incubated sample indicative of growth of the pathogen.

In another embodiment, the invention relates to a method for thedetection of a pathogen in a sample including the steps of determiningthe volume of a biological fluid sample in a sample container comprisingthe sample and a growth medium, comparing the sample volume to that of asample volume specification, if the sample volume is outside of thesample volume specification, providing a corresponding message,responding to any user input regarding the sample, then incubating thesample, and monitoring one or more parameters in the incubated sampleindicative of growth of the pathogen.

In another embodiment, the invention relates to a system for detecting apathogen in a sample, including an incubation and measurement moduleadapted to receive one or more sample containers comprising a biologicalfluid sample and a growth medium, a sample volume sensor, separate fromor part of said incubation and measurement module, the sensor adapted tomeasure the sample volume of said sample containers; and one or moreinterfaces adapted to perform one or more tasks selected from the groupconsisting of notifying a user if the sample containers are not withinpredetermined sample volume specifications, and accepting instructionson subsequent handling of the sample containers that are not withinpredetermined sample volume specifications.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a system employing multiple incubation andmeasurement instruments according to an embodiment of the presentinvention;

FIG. 2 is a detailed view of a measurement instrument employed in thesystem shown in FIG. 1 according to an embodiment of the presentinvention;

FIG. 3 is a top view of the measurement instrument shown in FIG. 2;

FIG. 4 is a conceptual schematic diagram of a sample volume sensor thatcan be employed in the instrument shown in FIG. 2 according to anembodiment of the present invention;

FIGS. 5A and 5B are conceptual schematic diagrams of a laserdisplacement sensor that can be employed in the instrument shown in FIG.2 according to an embodiment of the present invention;

FIGS. 6A and 6B are conceptual schematic diagrams of a through-beamoptical sensor that can be employed in the instrument shown in FIG. 2according to an embodiment of the present invention;

FIGS. 7A and 7B are conceptual schematic diagrams of a laserraster-scanning photodiode array that can be employed in the instrumentshown in FIG. 2 according to an embodiment of the present invention;

FIG. 8 is a conceptual schematic diagram of a capacitive sensor that canbe employed in the instrument shown in FIG. 2 according to an embodimentof the present invention;

FIG. 9 is a conceptual schematic diagram of a refractive index, internalreflection detection apparatus that can be employed in the instrumentshown in FIG. 2 according to an embodiment of the present invention;

FIG. 10 is a conceptual schematic diagram of a retro-reflective opticaldetection apparatus that can be employed in the instrument shown in FIG.2 according to an embodiment of the present invention;

FIG. 11 is a conceptual schematic diagram of a machine vision apparatusthat can be employed in the instrument shown in FIG. 2 according to anembodiment of the present invention;

FIG. 12 is a detailed view illustrating a sample volume sensor in usewith the measurement instrument shown in FIGS. 1-3; and

FIG. 13 is a signal processing flow diagram illustrating an exemplarymethod of implementing the sample volume sensor in use with themeasurement instrument shown in FIGS. 1-3.

FIG. 14 is a detailed view of an example of a detector assembly employedin the measurement instrument shown in FIGS. 1-3 which uses infraredlaser spectrography and/or dual wavelength modulation techniquesaccording to an embodiment of the present invention;

FIG. 15 is a side view of the monitoring assembly in FIG. 14;

FIG. 16 is a conceptual view of a multiple laser and multiple detectorarrangement employed in the monitoring assembly shown in FIGS. 14 and 15according to an embodiment of the present invention;

FIG. 17 is a block diagram of an example of the electronic componentsused by the monitoring assembly to monitor the concentration of one ormore gasses or pressure in the sample vials according to an embodimentof the present invention;

Throughout the drawings, like reference numerals will be understood torefer to like parts, components and structures.

DETAILED DESCRIPTION

A system 100 for detecting growth of microorganisms in sample culturesin which a sample volume sensor according to an embodiment of theinvention can be employed is shown in FIG. 1. The system 100 includes anumber of measurement instruments which can each use infrared laserspectrography and/or dual wavelength modulation techniques and/orindicator media to monitor the concentration of a gas such as oxygen orcarbon dioxide in sample vials, or to monitor the pressure in the samplevials, to detect microorganism growth in the vials.

As illustrated in FIG. 1, the system 100 includes a plurality ofincubation and measurement modules 102 that are connected to a centralcomputer 104. The central computer 104 can control factors, such as theincubation temperatures and times, as well as the timing of themeasurements performed by the modules 102, and can further collect andclassify the data readings obtained by the modules 102. The system 100can also include a data output device, such as a printer 106, which canbe controlled by the central computer 104 to print data readingsobtained by the incubation and measurement modules 102.

An embodiment of the incubation and measurement module 102 is shown inFIGS. 2, 3 and 14-17. Each incubation and measurement module 102 in thisembodiment includes a housing 108 and two shelves 110 that can be slidinto and out of the housing 108 in a direction along arrow A. Each shelf110 includes a plurality of openings 112, each of which is adapted toreceive a sample vial 114. The openings 112 are arranged in a pluralityof rows and columns as shown, and each shelf 110 can have any number ofopenings. For example, the openings 112 can be arranged in nine rows,with nine columns in each row, thus totaling 81 openings 112 per shelf110.

When a sample culture is to be analyzed by the incubation andmeasurement module 102, the sample culture is placed in a sample vial114. The sample vial 114 is then loaded into a respective opening 112 inthe incubation and measurement module 102. In the embodiment shown, thevial 114 is a closed sample vial having any number of suitable shapes ordimensions.

The incubation and measurement module 102 can further include akeyboard, a barcode reader, or any other suitable interface that enablesa technician to enter information pertaining to the sample into adatabase stored in a memory in the incubation and measurement module102, in the central computer 104, or both. The information can include,for example, patient information, sample type, row and column of theopening 112 into which the sample vial 114 is being loaded, and thelike.

According to the invention, the volume of a sample in the sample vial114, is determined for example, prior to placing the sample in theincubation and measurement module 102. For example, a hospital orclinical laboratory may handle dozens of patient samples per day for aspecific type of diagnostic test. These samples must be compliant withsample volume requirements so that the correct initial conditionsproduce validated test conditions under which the diagnostic method orsystem meet the manufacturer's specifications. Such compliance isrequired, as a number of patient samples may possibly contain relativelylow concentrations of the test target that is present in the sample, andoften the quantity of raw sample that is required may be quite difficultto obtain. Patient's who are anemic, very young, very old, or quite illmay not be able to supply a sufficient quantity of a sample, such asblood, that is needed. If an insufficient raw sample is obtained, thestatistical chance of recovering or detecting the target is reduced. Ifthe amount of raw sample is excessive, the growth of the target could besuppressed and therefore hinder detection.

In a typical application, a user such as a nurse, physician, ortechnologist, obtains the raw sample directly from a patient. The rawsample is then transported in a test container to a laboratory where itis analyzed for the presence of pathogens, either manually by eye, orautomatically by instrumentation. At this point, the invention allowsone to determine whether the quantity of the raw sample is sufficient toproduce reliable results. Alternatively, the sample volume may be usedto determine if special measurement or analysis techniques (i.e.,algorithms) should be applied in testing. Other applications of thesample volume are also possible.

For example, where practical, the laboratorian can scan the sample inthe test container using the apparatus of FIG. 4 to determine whether ornot the sample should be tested, or whether the sample is unlikely toproduce results that can be trusted. The laboratorian can thereafterprovide feedback to the hospital service that supplied the sample,requesting that another sample is required and that care should be takento assure compliance is achieved.

FIG. 4 is a schematic illustrating one embodiment of a system fordetermining the sample volume by detecting the height of the sample inthe vial 114. Specifically, the system of FIG. 4 measures the height ofthe liquid inside a culture vial 114 or other sample container using anultrasonic reflectometry apparatus (i.e., ultrasonic impulse sonar) andthereby, calculates the volume of the sample that the user introduces orinoculates.

To achieve the measurement noted above, the operator first places thepreviously inoculated container, vial or bottle into, for example, anappropriate receptacle in the module 102, or into a separate measuringapparatus that can be coupled to the module 102. The vial 114 remainssubstantially vertical and upright as it slides into a holder tube. Thebottom surface of the vial 114, either glass, polymer, or othermaterial, contacts a mildly compliant sonic coupler 164 at the bottom ofthe vial, which provides a waveguide for the high frequency sound from atransceiver 166, such as a 1 MHz Ultrasonic transceiver, into the vial114.

The sound, i.e., ultrasonic impulse, travels through the outer surfaceof the vial 114 and then to the liquid medium 165 within the vial 114.The liquid medium 165 can include a combination of growth media andblood. This sonic wave A then travels through the liquid medium 165within the vial 114 until part of it is reflected, as from a mirror, bythe interface between the liquid and the gas above the liquid. Part ofthe energy of the original sonic wave A then travels back through theinner and outer wall of the vial 114 until being conducted by thecompliant coupler 164 back to the transceiver 166.

A signal driver, amplifier, and processing circuit which is connected tothe transceiver 166 can then measure the length of time between eachevent. That is, from the time that the original sonic impulse isgenerated, to the time that the signal reflection returns and is sensed.This length of time is proportional to the height of the liquid medium165 inside the vial 114. Specifically, the signal driver, amplifier, andprocessing circuit can comprise an ultrasonic pulser/receiver 161coupled with the transceiver 166, and which is further coupled with anoscilloscope 163 to monitor amplified transceiver output waveforms, anda computer 167 to analyze the pulse echo to determine the vial samplevolume and generate a message or report. Such a report can then beprovided to the user as shown by the example message 170. Theoscilloscope can be used to illustrate the detected waveform signal 169showing sound reflections as output pulse returns from the liquid to airspace interface, however the oscilloscope can be replaced by signalanalysis circuits and/or signal processing software. Of course,appropriate calibration and normalization can be provided during thesignal processing calculations to account for differences in the liquidcontained within the container, normal sample volumes, temperaturefluctuations, container material, and so on, such that consistency insample volume determination is realized.

According to the invention, therefore, the quantity of a sample that hasbeen added to the culture vial or sample container can be determined,and this sample volume measurement data used for any number of purposes,such as to inform laboratory personnel concerning collection compliance,or to improve system performance through the foreknowledge of effectsthat may be expected when the sample volume is not optimal.

In the embodiment of FIG. 4, sample volume is measured using ultrasonicimpulse sonar. However, in other embodiments of the invention, themeasurement technique can include laser displacement sensing,through-beam optical sensing, ultrasonic reflectometry, and severalother methods described in greater detail below.

In a further embodiment, the ultrasonic impulse sonar measurementapparatus of FIG. 4 is replaced with a laser displacement sensingapparatus 200 as shown in FIGS. 5A and 5B. FIGS. 5A and 5B areconceptual schematic diagrams of a laser displacement sensor that can beemployed in the instrument shown in FIG. 2. In this embodiment, a laser,such as the diode laser 202 is aimed at a given angle toward the surfaceof the liquid 204 within the container or blood culture vial 206. Thelaser beam then returns to, and is sensed by, a linear detector, such asa linear array laser displacement sensor 208, which calculates thereturn angle trigonometrically. As shown in FIG. 5A, the laser-spot beamangle 210 is large. In FIG. 5B, the laser-spot beam angle 210 is small.This return angle corresponds to the height of the liquid within thecontainer (such as a low sample height as shown in FIG. 5A, a highsample height as shown in FIG. 5B, or any position therebetween) andtherefore, the volume can be determined given that the size and shape ofthe container 206 is a known constant.

According to another embodiment, a through-beam optical sensor apparatus220 is used to determine sample volume as shown in FIGS. 6A and 6B.FIGS. 6A and 6B are conceptual schematic diagrams of a through-beamoptical sensor that can be employed in the instrument shown in FIG. 2. Alight source, such as a linear light emitting diode array 222 isdirected through one side of a transparent or translucent container orblood culture vial 224. A linear detector, such as a linear photodiodearray or a linear imager charge coupled device (CCD) 226 on the oppositeside of the container 224 detects the difference in light intensity atthe meniscus, or the air/liquid boundary. A lightly shaded area 228illustrates that the light intensity striking the linear photodiodearray or CCD 226 is reduced by the contents' optical absorption. Thedetected interface position then indicates the fluid height (such as alow fluid height as shown in FIG. 6A, a high fluid height as shown inFIG. 6B, or any position therebetween) and hence, allows the accuratecalculation of the fluid volume within the sample container.

In another embodiment of the invention, a laser scanning, photodiodearray 240 is used to determine sample volume as shown in FIGS. 7A and7B. FIGS. 7A and 7B are conceptual schematic diagrams of a laserraster-scanning photodiode array that can be employed in the instrumentshown in FIG. 2. A linear photodiode array or CCD 242 is placed againstthe transparent or translucent outer wall of a sample container or bloodculture vial 244, and extends from one end to the other, across allpossible sample volumes within the sample container 244. The number anddensity of the photosensitive elements can be increased for higher levelresolution, or decreased for lower level resolution. During operation, alaser 246 is rotatably disposed adjacent to the sample container 244,and provides a scanning light through the sample container 244. Thelaser 246 scans the sample container 244 vertically through a rotationalong a path indicated by direction arrow 248. A lightly shaded area 245illustrates that the light intensity striking the linear photodiodearray or CCD 242 is reduced by the contents' optical absorption. Theresulting light intensity striking the photodiodes of array 242 isreduced by the contents' optical absorption. Accordingly, differentintensity measurements detected at the array 242 can then be used todetermine fluid height (such as a low fluid height as shown in FIG. 7A,a high fluid height as shown in FIG. 7B, or any position therebetween)and hence, allows the accurate calculation of the fluid volume withinthe sample container.

In still another embodiment of the present invention, a capacitiveproximity detection apparatus 260 is used to determine sample volume asshown in FIG. 8. FIG. 8 is a conceptual schematic diagram of acapacitive sensor that can be employed in the instrument shown in FIG.2. The apparatus includes electronics which rely upon the dielectricconstants of air, glass, and plastic, which are used for manywater-based liquid containers and which are much lower than that of thesample container contents. As the water or water-based liquid occupiesan increasing volume within a capacitive sensor's dielectric space, thecapacitance increases by an amount illustrated in equation (1) below.C=∈S/d  (1)

In equation (1), capacitance is equal to the relative dielectricconstant, ∈, times the surface area of the capacitor's plates, S,divided by the distance between the capacitor's plates.

In this embodiment, a capacitive sensor's plates can be fabricated as aflexible circuit disposed upon a substrate 262 such as mylar or kevlar.The substrate 262 allows the flexible circuit to be placed around anexterior of a sample container and excited by an RF sine wave via agenerator (not shown). The flexible circuit can be provided on thesubstrate 262 having a number of conductive circuit traces 270terminating in contact tabs 264 and 266. In this example, the contacttab 264 can be configured as a ground electrode for the flexiblecircuit, and the contact tab 266 can be configured as a sensingelectrode for the flexible circuit. The circuit traces 270 furtherprovide gaps 268, or a dielectric space, between conductors which formthe capacitive sensor. The liquid contents of the sample containeraround which the flexible circuit is placed then become a measurablefactor within the dielectric space, that is, as long as the samplecontainer's dimensions (such as wall thickness) are within a desiredrange as limited by the flexible circuit dimensions.

As the capacitance value increases due to the locally higher dielectricconstant of the fluid sample container contents, a decrease in thecapacitive reactance is experienced between the conductive circuittraces 270 and therefore, a measured AC current value provided to thecapacitive apparatus 260 increases. This measured AC current increasecan be sensed by a circuit element, such as a series drop resistor inthe RF power source, and can then be used to calculate the amount ofliquid level change within the sample container.

In still another embodiment of the invention, a refractive index,internal reflection detection apparatus 280 is used to determine samplevolume as shown in FIG. 9. A focused beam of light from either aconventional light source such as an LED, or a coherent source such as alaser 282, is directed at the side of the transparent, sample container284 and refracts as it transmits through the air to glass, or throughthe air to plastic interface of the sample container wall. The walls ofthe sample container 284 can be made of other materials, such ascrystalline quartz, silicon, borosilicate, and the like, however, aslong as the wavelength of the light can be transmitted with limiteddiffusion or absorption by the material.

The beam of light then refracts a 2^(nd) time coincident with the glassor plastic to liquid interface. The angle of light refraction isdependent upon the refractive indices of the materials on either side ofthe interface as noted by Snell's Law illustrated in equation (2) below.sin φ/sin φ′=n ₁ */n ₂*=constant  (2)For a wave's angle of incidence, φ, through a 1^(st) medium with arefractive index of n₁*, and an angle of refraction, φ′, through a2^(nd) medium with a refractive index of n₂*, the ratio of the tworefractive indices is equal to a constant.

A photodetector array 286 can then sense the change in position of therefracted beam 288 both before and after passage through the samplecontainer's contents to determine the position of the sample container'sfluid level, or the position of the interface between the liquid and theheadspace gas within the sample container 284.

In still another embodiment of the invention, a weight variationdetection apparatus (not shown) is used to determine sample volume. Thesample containers, which have relatively consistent weight from one toanother, are measured and evaluated. Specifically, the weight of asample container before the sample is added (known as an average weight)is determined and either stored in memory as a constant or loaded froman encoding within the barcode label. This weight can then be subtractedfrom the container's weight which is determined upon sample entry. Thisapproximate change in weight is proportional to the volume of sampleadded to the container.

For example, in the case of blood culture vials, the average vialpre-sample weight is the sum of the container weight with cap andseptum, the liquid media contents, the stirring element (if present),and the antimicrobial absorbing resin (if present). During themanufacturing process this weight can be held to within 1 gram from vialto vial. Therefore, the addition of blood to the vial during samplecollection can be calculated on a per sample basis within 1 milliliter.This is adequate to assure successful recovery of bacterial cells andinsure system performance.

In one implementation of the above embodiment, an operator would bedirected to measure the weight of the vial during the barcode readingprocess. Since barcode reading is performed in the normal workflow of alaboratory-based diagnostic instrument, no additional effort is requiredby the operator, and the sample volume data can be acquired at the sametime.

In still another embodiment of the invention, a retro-reflective opticaldetection apparatus 300 is used to determine sample volume shown in FIG.10. Instead of directing the beam of light through the sample containervolume as described above in regards to the through-beam optical sensorapparatus, the light beam can be sent into the side of the samplecontainer 302, and a retro-reflective change in the light level can thenbe sensed at the liquid-headspace gas interface. Specifically, a lightsource, such as a linear light emitting diode array 304 is shown throughone side of a transparent or translucent sample container or bloodculture vial 302. A linear detector, such as a linear photodiode arrayor CCD 306 on the same side of the sample container 302, then detectsthe difference in levels of reflectance at the meniscus, or theair/liquid boundary. The light will have different levels of reflectancedepending on the material within the sample container 302 where the beamis aimed.

In still another embodiment of the invention, a machine vision apparatus320 is used to determine sample volume as shown in FIG. 11. An automatedmachine vision system is provided including a camera 322 and imageprocessing program, which can visually determine the level of sample byintensity differences between the liquid within the sample container 324and the headspace gas, when the vial or sample container 324 is placedin a register with a datum point and then imaged.

In still another embodiment of the invention, an initial liquid levelindicator is used to determine sample volume. Specifically, a visual,magnetic, or other type of mark is stamped onto the side of the samplecontainer at the liquid to air interface point during manufacturing. Thedifference between the position of the “factory” mark and the currentliquid level is then determined as the amount of sample added. Anadvantage of this embodiment is that the accuracy can be improved byprecisely measuring the original level for each and every samplecontainer during their journey from filling to labeling and then topackaging.

In still another embodiment of the invention, a fluorescent volumeexclusion substance is used to determine sample volume. A fluorescent,luminescent, phosphorescent or other type of dye is added at a specificconcentration to the sample container's liquid contents at the time ofmanufacture. As sample is added during the collection process, the dyeis diluted from its original concentration. The difference between theinitial, nominal fluorescence, and the decreased fluorescence post-fill,is then detected and calculated to determine the volume of sampleintroduced into the container.

In still another embodiment of the invention, a method using the opticalscattering pattern caused by the hemoglobin in red blood cells (RBC's)is used to determine sample volume. In this embodiment, a laser beamdirected at a specific angle into the side of a blood culture containerwith added blood, forms a coma-shaped, light scattering pattern, andreflects part of the source energy. The appearance and shape of thisscattered light pattern is similar to that of a car's headlight whichforms a white orb as it is reflected in fog.

The intensity, breadth, length, decay and other parameters of thisscattered light source, or orb can be measured optically and is directlyrelated to the amount of blood introduced into the sample container. Anadvantage of this embodiment includes a desirable sensitivity to effectscaused by different patient's hematocrits in the resulting measurements.

In a similar embodiment, a method using optical absorption, allows auser to select a light wavelength which can be used to penetrate theliquid media plus blood to reach the other side of the sample container.A photodetector there measures the relative intensity of the lightgetting through the sample container and uses the information tocalculate the sample volume.

In still another embodiment of the invention, a nuclear magneticresonance (NMR) apparatus is used to determine sample volume. An NMRapparatus can be used to detect the intensity of hydrogen atom spin downcaused by magnetic impulse. The intensity of this signal is proportionalto the number and concentration of hydrogen atoms present. In the caseof a laboratory diagnostic as described herein, the hydrogen atoms wouldbe part of the water molecules and other organic materials containedwithin the container's liquid volume. The NMR signal taken before andafter sample fill can then be subtracted to calculate the sample volume.Additional information regarding an NMR detection apparatus is discussedin WO 99/67606, the entire content of which is incorporated herein byreference.

The above listing is not intended to be exhaustive, but is provided toillustrate the many techniques that can be applied to obtain the desireddiagnostic information. The above techniques, apparatus and applicationsinclude a number of advantages. For example, immediate feedback isautomatically obtained and provided to the laboratory personnel orinstrument operator e.g., when a sample volume is or is not withinspecification. If not within specification, the lab can for example,request another sample right away so that the patient's test results arenot delayed or worse, the patient's treatment is suboptimal resulting inincreased morbidity or mortality. Additionally, the summary data ofsample volume noncompliance, which can be automatically compiled andreported, can be used by the laboratory personnel to trace samples backto hospital services that have a high incidence so that remedial actioncan be used to elevate the quality of patient care.

According to an embodiment of the invention, the knowledge of samplevolume can also be applied to the interpretation of other test datataken by the system 100 to, in effect, optimize the automatic detectionalgorithms used. For example, in the case of blood cultures, a samplevolume higher than nominal contains a plethora of red blood cells whichadd their own metabolic activity to the metabolic activity frombacterial cells. Current blood culture instruments generally measure theproduction of carbon dioxide or oxygen either directly or indirectly bythe cells growing in the culture media. As the patient's blood adds itsown metabolic fraction, the fraction produced by any bacterial cellspresent can be obscured and result in a detection delay or error.Alternatively, if the blood volume added as a sample is low, the numberof living bacterial cells may also be low. The culture could grow muchslower than normal because of an insufficient biomass and therefore, toaugment detection sensitivity, the algorithms can be tunedappropriately.

The sensing and calculation of the sample volume can also be applied tohelp determine the initial concentration of an adjunct biochemical,particle, cell, and the like. For example, an immunoassay or molecularprobe test that is performed on the blood culture vial described abovecan quantify a constituent of the sample originally added (in this casethe patient's blood) to predict either the likelihood of no culturegrowth, definitive culture growth, or a coincident medical conditionsuch as Systemic Inflammatory Response Syndrome (SIRS).

The embodiments of the present invention described above can each beused to acquire additional information about the patient's sampleautomatically and apply that information to augment the utility of thediagnostic results.

One embodiment of the method of the invention is shown in FIG. 12. FIG.12 is a detailed view illustrating a sample volume sensor in use with ameasurement instrument such as that shown in FIGS. 1-3. The laboratoriancan place a filled sample container 402 into either the sample volumesensor of 404 or 406. In FIG. 12, the sample volume sensor 404 isconfigured as an internal sensor, disposed within the device 408, andthe sensor 406 is configured as an external sensor. The external sensor406 can then communicate sample volume and/or barcode information withthe device 408 via cabling, IR link, wireless communication, or thelike. The sample volume of the vial 402 can then be determined andassociated with the sample.

When a sample culture is to be analyzed by the incubation andmeasurement module, the sample culture is placed in a sample vial andthe sample vial is then loaded into a respective opening in theincubation and measurement module. The incubation and measurement modulecan further include a keyboard, a barcode reader, or any other suitableinterface that enables a technician to enter information pertaining tothe sample into a database stored in a memory in the incubation andmeasurement module, in the central computer, or both. The informationcan include, for example, patient information, sample type, row andcolumn of the opening into which the sample vial is being loaded, andthe like. FIG. 13 is a signal processing flow diagram illustrating thework flow associated with this embodiment.

In a first step of FIG. 13, a technician enters “Vial Entry” mode in thesystem software. The technician is then prompted to measure the samplevolume or “fill level” of the vial and read the associated barcode atstep 452. The technician then places the culture vial in a sample volumesensor and barcode reader at step 454. The system then reads the data ofthe barcode and determines a container media type which is used todefine an expected sample volume range at step 456. The culture vialsample volume is then measured by the reader at step 458. The samplevolume value can then be stored to provide data for compliance reportsat step 460.

The sample volume is then checked in steps 462 and 466. If the samplevolume is over specification value at step 462, an alternate backgroundfilter is applied at step 464. An alternate background filter woulddelay the signal processing algorithms from detecting evidence ofmicrobial growth. This is done so that the excessive blood fill and itseffects on the chemical environment within the culture vial would havean opportunity to stabilize and have less chance to be considered apositive culture (false positive) in the absence of true microbialgrowth. If the sample volume is not over specification value at step462, the sample volume is checked to determine if the sample volume isbelow specification value at step 466.

If the sample volume is below specification value at step 466, thesystem alerts the user that a replicate sample with higher blood volumemay improve recovery (i.e. the probability of detecting microbes) andasks the user to keep or reject the current sample at step 470. Thesystem then applies a positivity sense boost algorithm if the currentsample is used for the test. A positivity sense boost algorithm wouldincrease the sensitivity of the signal processing algorithms that detectevidence of microbial growth. This is done so that the lower thanoptimal blood fill and proportionally lower initial concentration ofmicrobes may be detected from more subtle signal changes.

If the sample volume is not below specification value at step 466, theuser is prompted to enter the culture vial into the test rack of theincubation and measurement module at step 472. The process is thenrestarted with the next culture vial at step 474, and returns to step452.

By evaluating the sample volume before the introduction of the sampleinto the testing queue of the laboratory several advantages are met.First, the laboratory is quickly made aware if the sample that wasforwarded is compliant with the culture vial manufacturer's packageinsert. Secondly, the sample compliance can be tracked to a particularhospital service or care-giver so that remedial training can beinitiated. Thirdly, the method of culture analysis and the algorithmsthat are used to determine the test result can be modified and enhancedto provide better performance, efficiency, and recovery. Fourthly, bysensing and quantifying a coexistent property of the patient sample byknowing the volume added, and the concentration of analyte tested, canlead to more definitive test results and in some cases, even further ormore specific diagnosis.

Additionally, the invention, though directly useful for blood culturesample handling, can be modified and applied to the collection of anysample into any sample container. In some cases, factors such asattenuation experienced in different media types may requireforeknowledge of the media type to apply the correct interpretivealgorithm.

In each technique described above, the results are generally superior tothose achieved by checking the sample volume by eye. For example,implementation of the ultrasonic impulse sonar measurement apparatusaccurately measures volumes to within 1.0 ml, and can compensate fordifferent sample container shapes, materials, original sample volumes,sample types, medium constituents, and so forth. This technique alsomeasures the liquid height and calculates the sample volume in a matterof seconds with a high degree of accuracy. This technique furtherexceeds the performance of some automated methods, such as weighing,since it avoids a possible variability in the mass of the containeritself as long as internal dimensions are held within nominal limits. Itis also noted that the container bottom does not need to be perfectlyflat or indented as shown in the attached figure. Nevertheless, in someapplications, volume measurement accuracy can be adversely affectedproportionally to extreme inconsistencies in the container uniformity.As can be appreciated from the above, the embodiments of the presentinvention solve the problems associated with varying media fill density,varying vial geometry, container material transparency, mixture ofsolid, liquid, and semisolid components in the container contents, anddifferences in the container material, whether plastic or glass.

As noted above, various techniques can be used in the embodiment of thepresent invention to determine the sample volume in a container withdifferent degrees of accuracy and repeatability, including evaluation byeye, by weight, by angle of light reflection, by optical absorption, bysonic ranging, by scattered photon migration, by chemical response, andso forth. These different methods can be provided individually or in anynumber of combinations to achieve the advantages as described above.

The embodiment of an incubation and measurement module shown in FIG. 3,is shown in more detail in FIGS. 14-16. The incubation and measurementmodule 102 includes a plurality of monitoring assemblies 116, which arepositioned in the incubation and measurement modules 102 to obtainreadings from the sample vials 114. In the embodiment shown in FIGS. 14and 15, each monitoring assembly 116 is configured to obtainmeasurements from the sample vials 114 inserted in two rows of openings112. However, the monitoring assembly 116 can be configured to obtainreadings from sample vials in any number of rows of openings as desired.

The monitoring assembly 116 includes a movable assembly 118 which, inthis example, is slidably coupled to a rail assembly 120 which isfixedly coupled to the top portion of shelf 110. A motor and pulleyassembly 121 comprising a motor 122, such as a DC servo motor, and apulley arrangement 123 that is driven by the motor 122, is coupled tothe rail assembly 120 and movable assembly 118. The motor 122 iscontrolled by, for example, the central computer 104 or a computer (notshown) in the incubation and measurement module 102 to drive the pulleyarrangement 123 which, in response, slidably drives the movable assembly118 along the rail assembly 120 in a sample vial reading directionindicated by arrow B in FIG. 14.

The moveable assembly 118 in this example further includes a sensor 124that can comprise, for example, a light emitting device 125 and a lightsensing device 126 positioned on opposite sides of a rail 127 of therail assembly 120. As the motor and the pulley assembly 121 drives themoveable assembly 118 along rail assembly 120, the sensor 124 detectsthe openings 128 in the rail 126, and provides a signal indicative ofthis detection to the central computer 104 or a computer in theincubation and measurement module 102. The central computer 104 or acomputer in the incubation and measurement module 102 uses thisdetection signal to monitor the position of the moveable assembly 118along the rail assembly 120. Also, because each opening 128 correspondsto a respective column of openings 112 in the shelf 110, the computercan determine which sample vials 114 are being read by the detectors inthe moveable assembly 118 of monitoring assembly 116 as described ingreater detail below.

The moveable assembly 118 can include a plurality of detector units 130,the number of which corresponds to the number of rows of sample vials114 that the monitoring assembly 116 is configured to read. That is, ifthe monitoring assembly 116 is configured to read two rows of samplevials 114, the movable assembly 118 will include two detector units 130.For illustration purposes, FIGS. 14 and 15 show only one detector unit130.

In an alternate arrangement, the movable assembly 118 can be configuredto scan in an x-y direction to take readings from the sample vials 114.That is, the movable assembly 118 can be configured to scan back andforth along the rows of sample vials 114 to therefore take readings fromthe entire array of sample vials 114.

As shown in FIGS. 14 and 15, each detector unit 130 includes at leastone laser 132 which, in this example, is an infrared diode laser, tomonitor the concentration of a gas or the pressure in the sample vials.The laser 132 is coupled to a laser assembly 134, which includes acooling and heating device 136 that can cool or heat the laser 132 totune the frequency of the light being emitted by the laser 132. As thelaser 132 emits light having a single frequency, a controller (e.g.,controller 154 shown in FIG. 7 and described in greater detail below)can control the cooling and heating device 136 to change this frequency,thus enabling the laser 132 to scan using a range of frequencies. Thelaser assembly 134 further includes a heat sink 138 that can dissipateheat from the cooling and heating device 136, and thus, aid incontrolling the temperature of the laser 132.

As further illustrated in FIG. 15, each detector unit 130 also includesa detector 140 that is mounted to receive the light being emitted by thelaser 132. In this example, the detector 140 is an infrared lightdetector capable of detecting infrared light having the wavelength(s) ofthe light emitted by the laser 132.

The laser 132, laser assembly 134, and detector 140, are coupled to alaser and detector mounting bracket 142, which is further coupled to amovable mounting bracket 144. The movable mounting bracket 144 iscoupled via slide rails 146 to a fixed mounting bracket 148. The fixedmounting bracket 148 is coupled with rail assembly 120 for movementalong the rail assembly 120 by the motor and pulley assembly 121.

A motor 150 is coupled to the movable mounting bracket 144 and iscontrolled by the central computer 104 or a computer in the incubationand measurement module 102, to move the movable mounting bracket 144 ina direction along arrow C as shown in FIG. 15. The motor 150 can thusposition the laser 132 and detector 140 at the appropriate locationalong the neck of sample vial 114 to obtain the most accurate readingsas discussed in greater detail below. Also, as can be appreciated fromthe above description, by moving the fixed mounting bracket 148 alongthe rail assembly 120, the motor and pulley assembly 121 translates theentire movable assembly 118, including the laser 132 and detector 140,in a direction along arrow B as shown in FIG. 14. This movementpositions the laser 132 and detector 140 at the necks of the samplevials 114 in the rows of sample vials 114.

In addition, for illustration purposes, FIGS. 14 and 15 each show only asingle laser 132 and a single detector 140. However, as shownconceptually in FIG. 6, the laser and detector mounting bracket 142 canhave a plurality of lasers 132 and a plurality of detectors 140 mountedthereto. In FIG. 16, three lasers 132 and three corresponding detectors140 are shown. As described in greater detail below, each laser 132 canemit infrared light having a particular wavelength based on the type ofgas that is to be detected in the sample vials 114. For example, onelaser 132 can emit infrared laser light having a wavelength appropriatefor detecting carbon dioxide, another laser 132 can emit infrared laserlight having a wavelength appropriate for detecting oxygen, and thethird laser 132 can emit infrared laser light having a wavelengthappropriate for detecting another type of gas. Also, each detector 140is disposed at an opposing position to detect light from a respectivelaser 132 as shown.

FIG. 17 is an exemplary schematic illustrating the components providedfor reading a sample vial 114 in accordance with an embodiment of thepresent invention. As shown in FIG. 17, once a laser 132 andcorresponding detector 140 have been positioned with respect to a samplevial 114 to be read, a computer 152, which can be included in thecentral computer 104 or in incubation and measurement module 102,controls a laser controller 154 to control the laser 132 to emit aninfrared laser light toward the neck of the sample vial 114. The laserlight that passes through sample vial 114 is detected by detector 140,which converts the detected laser light into an electrical signal andprovides the electrical signal to an AC preamplifier 156. As can beappreciated by one skilled in the art, the AC preamplifier 156 performsan AC amplification on the electrical signal and provides the amplifiedsignal to a DC preamplifier 158 and a lock-in amplifier 160. The DCpreamplifier 158 and the lock-in amplifier 160 further amplify theelectrical signal and provide the further amplified electrical signal tothe computer 152.

The computer 152 receives and interprets the amplified signal todetermine whether any of the infrared laser light emitted by laser 132has not been detected by detector 140, thus indicating that some of thelaser light has been absorbed by a gas within the sample vial 114. Thecomputer 152 can thereafter, determine the type and concentration of thegas and, if desired, the pressure inside the sample vial 114 based onthe amplified electrical signal using suitable algorithms as describedin detail in the U.S. Pat. No. 6,709,857 referenced above.

While various embodiments have been chosen to demonstrate the invention,it will be understood by those skilled in the art that variousmodifications and additions can be made without departing from the scopeof the invention.

1. A system for detecting a pathogen in a sample, comprising a pluralityof sample containers comprising a growth medium and adapted to receive abiological fluid sample; an incubation and measurement module comprisinga plurality of individual openings, each opening adapted to receive oneof the plurality of sample containers; a sample volume sensor, separatefrom or part of said incubation and measurement module, the sensoradapted to measure the sample volume of said sample containers; and oneor more interfaces adapted to perform one or more tasks selected fromthe group consisting of (a) notifying a user if said sample containersare not within predetermined sample volume specifications, (b) acceptinginstructions on subsequent handling of said sample containers that arenot within predetermined sample volume specifications, and (c) promptinguser to place said sample container into a test rack of said incubationand measurement module if sample volume is within sample volumespecification.
 2. The system of claim 1 wherein said sample volumesensor is part of said incubation and measurement module.
 3. The systemof claim 1 wherein said sample volume sensor is separate from saidincubation and measurement module.
 4. The system of claim 1 furthercomprising a computer for notifying the user if said sample containersare not within predetermined sample volume specifications and forprompting the user for a response.
 5. The system of claim 1 furthercomprising a computer for applying an algorithm to augment detectionsensitivity, if said sample volume is less than said sample volumespecification.
 6. The system of claim 5, wherein said algorithm is apositivity sense boost algorithm.
 7. The system of claim 1 furthercomprising a computer for applying an alternate background filter, ifsaid sample volume is greater than said sample volume specification. 8.The system of claim 1 wherein said interfaces are at least one componentselected from the group consisting of a keyboard and a barcode reader.9. The system of claim 1 wherein said sample volume sensor comprises anultrasonic reflectometry apparatus.
 10. The system of claim 1 whereinsaid sample volume sensor comprises a laser displacement sensingapparatus.
 11. The system of claim 1 wherein said sample volume sensorcomprises a through beam optical sensor apparatus.
 12. The system ofclaim 1 wherein said sample volume sensor comprises a laser scanningphotodiode array.
 13. The system of claim 1 wherein said sample volumesensor comprises a refractive index, internal reflection apparatus. 14.The system of claim 1 wherein said sample volume sensor comprises aweight variation detection apparatus.
 15. The system of claim 1 whereinsaid sample volume sensor comprises a retro-reflective optical detectionapparatus.
 16. The system of claim 1 wherein said sample volume sensorcomprises a machine vision apparatus.
 17. The system of claim 1 whereinsaid sample volume sensor comprises a capacitive proximity detectionapparatus.
 18. The system of claim 1 wherein said sample volume sensorcomprises a fluorescent, luminescent or phosphorescent detectionapparatus.
 19. The system of claim 1 wherein said sample volume sensorcomprises an optical scattering apparatus.
 20. The system of claim 1wherein said sample volume sensor comprises a nuclear magnetic resonanceapparatus.